The present invention relates to an electromagnetic fluid valve used for controlling fluid such as air, and more particularly to an electromagnetic fluid control valve used for selectively opening or closing a controlled fluid (air) pipe of a canister constituting an evaporated fuel purge system which is usually associated with a fuel tank of an automotive vehicle.
Unexamined published Japanese patent application No. 7-233882 discloses an electromagnetic fluid control valve comprising a controlled fluid passage, a solenoid coil (i.e., an electromagnetic actuator), and a diaphragm partitioning the controlled fluid passage and the solenoid coil. The diaphragm, having a constant film thickness, is disposed between an axial end of a movable member and a coil retaining member.
More specifically, according to the valve arrangement disclosed in the unexamined published Japanese patent application No. 7-233882, the solenoid valve selectively blocks and unlocks communication between a first passage and a second passage. The solenoid valve includes a stationary iron core, a first movable member, and a second movable member. The stationary iron core is magnetized when a coil is energized. The second movable member is made of a permanent magnet. The magnetic poles of the permanent magnet are arranged in such a manner that the permanent magnet repels the stationary iron core when the coil is energized. As the second movable member moves, the first movable member comes into contact with a valve seat defining a portion of the second passage. When the first movable member is in contact with the valve seat, communication between the first passage and the second passage is blocked.
An operation chamber extends between the first movable member and the second movable member. The first movable member includes a valve member and an annular diaphragm. The annular diaphragm extends radially outward from the valve member. Thus, the inner circumferential edge of the diaphragm is connected with the valve member. The outer circumferential edge of the diaphragm is connected with a coil hold member. The valve member is movably supported by the diaphragm. The valve member has a first through hole for providing communication between the operation chamber and the second passage. The diaphragm has a second through hole for providing communication between the operation chamber and the first passage. When the valve member departs from the valve seat, the operation chamber and the second passage communicate with each other via the first through hole. When the valve member is in contact with the valve seat, the first through hole is closed by the second movable member so that the operation chamber and the second passage are disconnected from each other. On the other hand, the operation chamber and the first passage remain in communication with each other via the second through hole regardless of condition of the valve member which departs from or contacts to the valve seat.
Unexamined published Japanese patent application No. 8-312827 discloses an electromagnetic fluid control valve including a coil, a moving core, and a yoke. A coil hold member supports the coil. The moving core moves as the coil is energized and de-energized. The yoke has a valve portion formed with a communication hole and a valve seat around the communication hole. A valve rubber is mounted on the moving core. When the coil is de-energized, the moving core is positioned by a return spring so that the valve rubber is separate from the valve seat. Thus, in this case, the communication hole is unblocked. When the coil is energized, the moving core moves toward the valve portion of the yoke and the valve rubber comes into contact with the valve seat. Thus, in this case, the communication hole is blocked. The moving core has a cylindrical portion extending into a central bore of the coil hole member.
However, according to the former electromagnetic fluid control valve, the diaphragm having a constant film thickness isolates the electromagnetic actuator from the controlled fluid passage. Thus, it becomes possible to prevent water or other foreign substances contained in the controlled fluid from entering into the electromagnetic actuator. However, when the first movable member operates, there is a tendency that the first movable member itself may incline with respect to its operating direction. Such an inclined movement of the first movable member leads to leakage of controlled fluid in the closed state of the valve.
Furthermore, according to the latter electromagnetic fluid control valve, a shaft is supported at only one end by the coil hold member serving as bearing portion of the moving core. The shaft easily inclines with respect to the its operating direction. When the shaft inclines, the valve attached to the front end of this shaft contacts with a sheet in an inclined manner. This will lead to the leakage of controlled fluid. Furthermore, when the moving core operates, the sheet rubber provided in the moving core is brought into contact with the bottom of the yoke and causes noise sound.
To solve the above problems, the present invention has an object to provide an electromagnetic fluid control valve capable of providing excellent sealing between the shaft and the valve member as well as excellent sealing between the shaft and the diaphragm.
Furthermore, the present invention has an object to provide an electromagnetic fluid control valve which provides a simplified shaft arrangement.
Moreover, the present invention has an object to provide an electromagnetic fluid control valve which is capable of improving the assembling works and realizing cost reduction.
In order to accomplish the above and other related objects, the present invention provides an electromagnetic fluid control valve comprising an electromagnetic actuator having a movable member slidable in an axial direction of the electromagnetic fluid control valve. A valve body has an accommodation chamber storing the electromagnetic actuator therein, a fluid passage in which fluid flows, and a valve opening formed in an appropriate portion of the fluid passage. A diaphragm airtightly separates an inside space of the valve body into the fluid passage and the accommodation chamber. A shaft extends in the axial direction through the valve opening and is integrally shiftable with the movable member in the axial direction. The shaft has a flange at one axial end thereof which is capable of passing through the valve opening. A valve member is coupled around the shaft at one axial end for closing the valve opening when the valve member is brought into contact with a valve seat formed around the valve opening and for opening the valve opening when the valve member lifts off the valve seat. A retainer is coupled around the shaft at a portion axially offset from the valve member. The retainer is capable of passing through the valve opening. A first retaining portion is provided at one axial end of the retainer, with the valve member sandwiched between the flange of the shaft and the first retaining portion of the retainer. And, a second retaining portion is provided at the other axial end of the retainer, with the diaphragm sandwiched between the movable member of the electromagnetic actuator and the second retaining portion of the retainer.
According to a preferred embodiment of the present invention, it is preferable that the valve member has at least one ring-shaped projected portion provided on an end surface thereof, and the ring-shaped projected portion is deformed when a pressing force is applied between the flange of the shaft and the first retaining portion of the retainer.
Furthermore, it is preferable that at least one ring-shaped projected portion is provided on both end surfaces of the valve member. The valve member has two circular ridges as at least one ring-shaped projected portion.
Furthermore, it is preferable that the valve body has a stopper for restricting an excessive shift movement of the shaft in the axial direction when the electromagnetic valve is in an opened state.
Furthermore, it is preferable that the stopper is formed on a partition wall protruding radially inward from a tubular wall of the valve body for separating the fluid passage into two passages.
Furthermore, it is preferable that an inner circular edge of the partition wall defines the valve opening.
Furthermore, it is preferable that the retainer has a central projection formed between the first retaining portion and the second retaining portion, and the central projection is brought into contact with the stopper of the valve body when the electromagnetic valve is in an opened state.
Furthermore, it is preferable that the central projection of the retainer includes a plurality of legs extending in radially outward directions from a main body of the retainer.
Furthermore, it is preferable that the first retaining portion has a flat surface extending perpendicularly to the axial direction for providing surface contact between the valve member and the retainer.
Furthermore, it is preferable that the second retaining portion has a flat surface extending perpendicularly to the axial direction for providing surface contact between the diaphragm and the retainer.
Furthermore, it is preferable that the electromagnetic fluid control valve further comprises a communication passage for providing connection between the accommodation chamber and the outside of the valve body.
Furthermore, it is preferable that the communication passage includes an orifice which substantially restricts a flow rate of fluid in the communication passage.
Furthermore, it is preferable that the diaphragm has a central portion and an easily deformable portion extending around the central portion, and the central portion has a higher rigidity than the easily deformable portion.
Furthermore, it is preferable that the central portion of the diaphragm is coupled around the solenoid shaft.
Furthermore, it is preferable that the central portion of the diaphragm is thicker than the easily deformable portion extending around the central portion.
Moreover, the present invention provides a method for assembling the above-described electromagnetic fluid control valve. The assembling method comprises a first step of coupling the valve member around one axial end of the shaft by inserting the other axial end of the shaft into an engagement hole of the valve member, a second step of combining the valve body with the shaft by inserting the other axial end of the shaft into the valve opening of the valve body so that the shaft extends through the valve opening of the valve body, a third step of coupling the retainer around the shaft by inserting the other axial end of the shaft into an engagement hole of the retainer, a fourth step of coupling the diaphragm around the shaft by inserting the other axial end of the shaft into an engagement hole of the diaphragm, and a fifth step of coupling the movable member of the electromagnetic actuator around the other axial end of the shaft by inserting the other axial end of the shaft into an engagement hole of the movable member.